While consumers are notoriously fickle about the brands they buy, they can be adamant about the ones they don't buy. In a survey conducted for Adweek by Alden & Associates Marketing Research of Hermosa Beach, Calif., 49 percent of respondents said they make a point of not buying certain brands when they shop. What is it that makes a brand non grata with consumers? Among respondents who said they avoid a brand, 81 percent attributed this to a bad personal experience with it. Another 11 percent reported being influenced by "what others say," while 8 percent cited both factors. There's an asymmetry that tends to swell the ranks of the anti-brand loyalists: People who use a brand are liable at any time to have a bad experience with it, while those who shun a brand are in no position to have a good experience with it. Can delightful advertising prompt consumers to forgive a brand for past sins? So one would like to think, although lousy ads in the brand's past are probably conspicuous among those sins.